Such a capped lamp/reflector unit is known from U.S. Pat. No. 4,626,734. Units of this type may for example be used for projection purposes, for example film or slide projection or projection television devices. In these applications generally a compact filament lamp or a compact high-pressure mercury discharge lamp is used with a short arc length, for example an arc length in the range of about 0.5 mm to 3 mm. In particular for the high pressure discharge lamp, relatively high voltages, typically in the range of several kVolts, are required to (re-)ignite the lamp. As a result, particularly upon (re-)ignition of the lamp there is a risk of flashover between the electrical contacts. Besides, these lamps are becoming more and more available to the consumer market, for example in beamers for slide shows in home applications. Upon failure of the lamp/reflector unit, replacement of the unit should be enabled to the layman. In the known unit, the capped electric lamp/reflector unit must be taken out of the holder in an axial direction, which involves the disadvantage that replacement of the unit is rather complex. It is a further disadvantage of the known unit that it is still relatively unsafe, as the lamp cap has both electrical contacts provided relatively close to one another.